Christmas Day Severe Nor'easterWednesday into early Thursday Morning December 25-26, 2002

The tremendous amount of snow produced by this classic winter
storm is going down into the record books at Albany as being among the top ten largest
dumps since records began in 1885. An official storm total of 21 inches was recorded
at the CESTM building on the SUNY campus in Albany making it the 9th greatest snowfall on
record in any month for the city. The 21 inch amount was also sufficient to rank the
storm the 4th largest in December. And the 19.2 inches of snow that fell on December
25 smashed the previous Christmas day record snow at Albany of 11.8 inches which fell in a
large storm in 1978. Snowfall amounts climbed to as high as 36 inches in parts of
southern Herkimer and Otsego counties with widespread reports of 20"-25" in a
zone that extended from northeast Pennsylvania, through the Catskills, Mohawk valley,
Capital/Saratoga, regions to southern Rutland and Bennington counties in Vermont.

Snow began as light intermittent patches between 6:00am and
8:00am across much of the area. Generally light snows occurred through much of the
region through the mid to late morning hours with a gradual increase in coverage and
intensity by noon. Initially a period of sleet and freezing rain occurred in the mid
Hudson valley to Berkshire county, MA during the morning. Lighting and thunder
occurred in the area of mixed precipitation as low pressure began rapidly intensifying
along the coast. With the storm exploding east of New Jersey bands of exceptionally
heavy snow began forming and rotating northwest away from the storm center through the
area between 1:30pm and 9:00pm. Snowfall rates climbed to between one and two inches
per hour over much of the region with a periods of up to incredible five inch per hour
snowfall rates. The most intense snow band cranked snow out at five to six inches
per hour during the late afternoon and evening over the Catskills and Mohawk valley during
the late afternoon and evening. That band of blinding snow pivoted through the
Capital Region during the evening and eventually ended up in western New England between
8:00 and 10:00pm in a somewhat weakened form. By midnight snowfall rates decreased
to an average of 1/2" per hour in patches. By 4:00am all but the last of the
flurries had ended in the area leaving one of the most widespread deepest snowfalls in
this area since the March 1993 blizzard. Although, winds did gust to 35 mph with
this storm creating widespread blowing and drifting snow as well as whiteout zero
visibility conditions, the duration of the wind and poor visibility was considerably
shorter and less severe than what occurred in the March 1993 storm.

This storm, like most of the weather systems to affect the
Northeast this season to date originated in the very active southern jet stream
branch. (A moderate El Nino condition existing in the equatorial Pacific, where
warmer than typical sea surface temperatures exists, leads to an enhanced sub-tropical jet
stream and thus stronger than normal southern jet stream branch storms.)

The storm originally developed over the southwest U.S. as an
upper air system on Saturday, December 21. This parent upper air storm, driven
completely by the powerful sub tropical jet stream, then pulled out of the southwest over
the weekend producing a surface area of low pressure over south Texas Monday afternoon.
Warm moist air riding north ahead of the system in concert with the powerful jet
lead to several episodes of violent thunderstorms over south Texas and the gulf coastal
region as well as Alabama, southern Georgia, and Florida from Sunday afternoon through
Tuesday morning, December 22-24. By late Tuesday, the primary surface low tracked
northeast into the Tennessee river valley with a weak low forming along the mid Atlantic
coast. This weak low shot out to sea south or our region but did produce some very
light snow and flurries across southern New England Christmas eve. By Christmas
morning, the primary surface low responsible for the heavy rains and severe weather
outbreaks across the Gulf coast, and a swath of 10 inch snows across Missouri, southern
Illinois, and Ohio, had moved into western Pennsylvania in a weakening state. This
storm's energy was transferring to the coast, where the low that became the severe
Nor'easter for this region, was forming. Explosive storm development occurred along
the New Jersey coast during the Christmas morning and afternoon as the upper air storm
interacted with the temperature contrast zone along the coast and strong jet stream winds,
to cause a rapid expansion of rain near the coast and snow over the central New York and
northeast Pennsylvania.

As the storm began it's rapid intensification along the
coast, at one point deepening by a huge 10 millibars per hour, enough mid level warm air
circulated into the mid Hudson valley and Berkshire county to allow a several hour period
of mixed snow, sleet, and freezing rain to occur. However, the rapid accent of air
in the atmosphere as the storm bombed out more than sufficiently created an environment of
local cooling to allow the mixed precipitation to change to heavy wet snow. The
interaction of ice and water as well as strong accent in the atmosphere, helped to create
some lightning and thunder through the morning in the zone of mixed precipitation. (It is
not unusual for lightning and thunder to occur in association with rapidly deepening
winter storms.) Snowfall rapidly expanded in coverage and intensity after 1:00pm.
Several banded features developed with the storm and pivoted away from the center
into eastern New York and western New England through it's duration. Snowfall rates
in the bands, ranged from two inches per hour to an incredible five inches per hour by the
late afternoon and evening leaving tremendous snow accumulations ranging from 24-36"
in the hardest hit regions of Otsego, Delaware, Montgomery, and western Albany counties.

The storm's structure was one of an extremely tightly wound
compact system. The observed snowfall distribution map below illustrates how tight a
system it was with a very sharp gradient of accumulations in the region. Notice how narrow
the zone of heaviest snow was across eastern New York and western New England and how
sharply the snow accumulations to the north and west of the blitz zone dropped off. (The
slightly reduced snowfall amounts south and east of the Capital Region can be partially
attributed to the period of mixed precipitation early in the storm and a somewhat removed
position from the zone of maximum lift that set up with this system in the atmosphere.)
It is not unusual for powerful storms of this nature to have very tight gradients
of precipitation and is an example of how a forecast track error of as little as fifty
miles can sometimes mean the difference between a few inches of snow vs. upwards of thirty
inches of snow. The other interesting and somewhat unique feature of the storm was
the rate at which the snow piled up. Most of the top twenty heaviest snowstorms at
Albany occurred over several days . This storm, however, produced an average of two feet
of snow through the Capital Region in an incredible ten hours!

As the storm deepened an initially NNE wind over the region
shifted into the NNW and finally the NW and increased to 20-35 mph with gusts in it's wake
over exposed mountains the following day to 45 mph. Temperatures through the
duration of the storm held steady in the middle to upper 20's yielding a fairly dry, light
snow, that was very susceptible to blowing and drifting. The blowing and drifting
snow lead to particularly bad visibility with frequent whiteout conditions across the
region through Christmas night.

Observed Snowfall Distribution Map For
the Christmas 2002 Storm

(This graphic was created using snowfall
data collected by WRGB's exclusive WeatherNet 6 weather spotter network as well as
observations from the NWS cooperative observer network)

Town By Town Storm Totals from WeatherNet 6 Spotters
and National Weather Service Cooperative Observers for the Christmas 2002 Storm